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Air Emissions Damages from Municipal Drinking Water Treatment Under Current and Proposed Regulatory Standards Daniel B Gingerich, and Meagan S Mauter Environ. Sci. Technol., Just Accepted Manuscript • DOI: 10.1021/acs.est.7b03461 • Publication Date (Web): 23 Aug 2017 Downloaded from http://pubs.acs.org on August 25, 2017

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Air Emissions Damages from Municipal Drinking Water Treatment Under Current and

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Proposed Regulatory Standards

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Daniel B. Gingerich1 and Meagan S. Mauter1,2,* 1

Department of Engineering and Public Policy, Carnegie Mellon University, Pittsburgh, PA 15213 2 Department of Civil and Environmental Engineering, Carnegie Mellon University, Pittsburgh, PA 15213 *Contact Author: [email protected] Abstract Water treatment processes present inter-sectoral and cross-media risk trade-offs that are

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not presently considered in Safe Drinking Water Act regulatory analyses. This paper develops a

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method for assessing the air emission implications of common municipal water treatment

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processes used to comply with recently promulgated and proposed regulatory standards,

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including arsenic, lead and copper, disinfection byproducts, chromium (VI), strontium, and

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PFOA/PFOS. Life-cycle models of electricity and chemical consumption for individual drinking

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water unit processes are used to estimate embedded NOx, SO2, PM2.5, and CO2 emissions on a

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cubic meter basis. We estimate air emission damages from currently installed treatment

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processes at US drinking water facilities to be on the order of $500 million USD annually. Fully

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complying with six promulgated and proposed rules would increase baseline air emission

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damages by approximately 50%, with three-quarters of these damages originating from chemical

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manufacturing. Despite the magnitude of these air emission damages, the net benefit of currently

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implemented rules remains positive. For some proposed rules, however, the promise of net

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benefits remains contingent on technology choice.

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1.0 Introduction The Safe Drinking Water Act (SDWA) provides regulatory authority to the US federal

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government to create enforceable standards for drinking water quality and safety.1 These

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standards have enabled extraordinary gains in public health,2 and retrospective analyses of

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historic drinking water quality regulations indicate that the benefits have far exceeded any

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compliance costs.2, 3 Fully assessing these benefits and costs for emerging drinking water

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contaminants is more challenging, particularly when contaminant removal processes impose

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systemic risk tradeoffs.4

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The most notable example of these risk trade-offs in drinking water regulatory analyses is

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for disinfection and disinfection byproducts. In establishing the Long-Term Enhanced Surface

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Water Treatment Rules,5 the EPA set regulatory standards to balance the competing risks of

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acute illness from microbial contamination with the risks of cancer from disinfection

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byproducts.6 There is also a growing body of research on inter-sectoral risk trade-offs involving

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drinking water, including the use of methyl tert-butyl ether (MTBE) as a gasoline additive,7

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bromide for mercury control at power plants,8, 9 and atrazine as a pesticide.10 But the

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incorporation of inter-sectoral and inter-media (e.g. water and air or water and soil) trade-offs

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into regulatory analyses is often limited by the “bounded oversight” of the regulators responsible

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for designing drinking water regulations.7, 11 Researchers have argued that benefit-cost analysis

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can address bounded oversight to express the benefits and damages to a variety of media.12, 13

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Even with benefit-cost analysis, however, an analyst must make a deliberate choice to include

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cross-media impacts in the scope.

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Drinking water regulatory analyses have also neglected to consider trade-offs that occur over the life-cycle of the water treatment system, most notably the operation phase. Drinking

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water systems comply with SDWA rules by installing separation processes that rely on

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electricity and chemicals.14, 15 Life-cycle assessments (LCAs) of drinking water systems have

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demonstrated that the majority of impacts associated with drinking water treatment occur as a

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result of electricity and chemical consumption during plant operation.15-18 These impacts include

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emissions of greenhouse gasses (GHGs) and the criteria air pollutants (CAPs) NOx, SO2, and

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particulate matter from electricity generation and chemical manufacturing. These indirect

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emissions of GHGs and CAPs produced over the life cycle of water treatment impose human

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health, environmental, and climate (HEC) damages.19-23

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While there are a multitude of drinking water treatment LCAs that quantify the energy

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intensity or GHG and CAP emissions from water treatment,15-17, 24-29 we are unaware of any that

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quantify the human health damages associated with these emissions. Furthermore, the vast

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majority of these LCAs were performed for a single treatment train, rather than for the diverse

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set of processes currently installed at drinking water treatment facilities around the US. Accurate

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estimates of the air emission damages from US water treatment plants under current and future

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regulatory scenarios is further confounded by the high regional variability in the emissions

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factors associated with chemical and electricity process inputs. In the absence of quantitative

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methods for estimating air emission damages from existing and emerging water treatment

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processes, rulemaking activities have been unable to consider competing risks from diminished

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air or water quality.

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This work fills this gap by developing and applying a quantitative method for evaluating

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the life-cycle air emission damages from drinking water treatment. We build life-cycle models

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of electricity and chemical consumption for drinking water unit processes, estimate the

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embedded smokestack emissions of NOx, SO2, PM2.5, and CO2, and provide spatially resolved

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estimates of associated damages to human health and the environment. We apply this

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methodology to estimate the air emission damages from installed water treatment processes at all

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US drinking water facilities. Finally, we evaluate the air-water risk tradeoffs for six proposed

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and promulgated drinking water regulations.

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2.0 Methods

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2.1 Estimating Air Emission Damages from Drinking Water Treatment

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To calculate the air emission damages associated with drinking water treatment processes

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we combine treatment level-facility data with state-level data on electricity consumption,

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chemical manufacturing, and air emission damages (Figure 1).

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Figure 1. Method for calculating the drinking water air emission damages and net benefits or

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net costs for the regulations included in this analysis.

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For this analysis, we focus on six different contaminant/regulations and compliance

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technologies: Arsenic,30 Lead and Copper,31 Disinfectant By-Products (DBPs),5 Hexavalent

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Chromium,32 Strontium,33 and Perfluorooctanoic Acid (PFOA) and Perfluorooctyl Sulfonate

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(PFOS)34 (Table 1, Supporting Information Section 1.0). Three of these rules (Arsenic, Lead and

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Copper, and DBP) are finalized. The other three rules, Hexavalent Chromium, Strontium, and

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PFOA/PFOS, are at various stages in the regulatory process. These rules will require the

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installation of new treatment processes at non-compliant facilities. Analysis on the air emission

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impacts of regulations considers only the effects of installing new processes at non-compliant

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plants to meet proposed standards. If a facility already has a compliance technology installed

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and is compliant with the standard, we do not consider it in evaluating the air emissions

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associated with complying with that rule.

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Table 1. Rules and Compliance Technologies Rule

Compliance Technologies

Arsenic Iron Co-Precipitation Lead and Copper Corrosion Inhibitor DBP

GAC Adsorption

Chromium (VI) Strontium PFOS/PFOA

Reverse Osmosis Lime Soda Ash Softening Reverse Osmosis / GAC Adsorption

Standard 10 ug/L Lead 15 ug/L Copper 1.3 mg/L TTHM 80 ug/L HAA5 60 ug/L 10 ug/L 1.5 mg/L Total 70 ng/L

Number of Non-Compliant Systems 1,086 2,757 1,697 25 113 27,000

99 100

Drinking Water System Data

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We use data from the Safe Drinking Water Information System (SDWIS),35 Unregulated

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Contaminant Monitoring Rule (UCMR),36 and Information Collecting Rule (ICR) 37 (SI Section

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2.0) to identify the (1) state, (2) installed treatment technologies (SI Section 3.0), and (3) volume

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of water. In total, 47,500 drinking water systems serving 288 million people were analyzed.

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We use the location of each facility reported in SDWIS to identify the appropriate statelevel marginal emissions factor38 for generating electricity used during water treatment. SDWIS

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also identifies currently installed treatment processes that we use in developing a model of

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baseline emissions from drinking water treatment. SDWIS does not report water production, and

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so we estimate total annual water production for system i, Vi [m3/yr], as the product of SDWIS

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reported population served, Popserved [person], and the state-level average per capita water

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consumption per year, Apc [m3/person·yr],39 as shown in Equation 1. 𝑉𝑖 = 𝐴𝑃𝐶 𝑃𝑜𝑝𝑖,𝑠𝑒𝑟𝑣𝑒𝑑 (1)

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We determine facilities that will need to install additional treatment technologies to

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comply with the six water quality rules (Table 1) by comparing the MCL for each rule to water

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quality data reported in the UCMR and the ICR. If water quality data is not available for a

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facility, we apply state-averaged water quality data for that facility. We assume that any

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compliance technologies that are installed are operated to in order to achieve compliance with

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the regulation.

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Life-Cycle Inventory of Air Emissions from Drinking Water Systems

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For each facility in our dataset, we use SDWIS35 to inventory the water treatment

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technologies currently installed in the “baseline” treatment train. For non-compliant systems, we

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also inventory technologies necessary to bring a “regulated” treatment train into compliance with

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each of the six pending or proposed water quality rules (SI Section 1.0). Average electricity27, 40

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and chemical inputs15, 27, 41 for each of these treatment processes is obtained from the published

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literature and reported in SI Sections 2.0 and 3.0 and Tables S1-S3. Finally, we estimate the air

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emissions embedded in these electricity and chemical inputs in the year 2014.

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𝐸𝑙𝑒𝑐 The mass of annual air emissions associated with electricity consumption, 𝑀ℎ,𝑖,𝑗 [g/yr] is

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calculated for each pollutant j from drinking water facility i under scenario h of either the

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baseline scenario or new regulation scenario using Equation 2. Emissions are the product of the

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volume of water produced at facility i, Vi [m3/yr], the total electricity consumption of the unit

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processes, g, that are installed in the baseline or newly-regulated scenario, h, Eg,hW [kWh/m3], and

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the marginal emissions factors per kWh for air pollutant j in state l, emf,j,l [g/kWh].38, 42 The

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emissions factors for CO2, NOx, and SO2 are marginal emission factors, as only a small

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percentage of US electricity generation is consumed by water treatment processes.43, 44 Marginal

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emission factors are not available for PM2.5 and so we use state-level average emission factors

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from the EPA Emission Inventories.42 Electricity is assumed to be generated in the state where

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the drinking water facility is located. 𝐸𝑙𝑒𝑐 𝑊 𝑀ℎ,𝑖,𝑗 = 𝑉𝑖 𝐸𝑔,ℎ 𝑒𝑚𝑓,𝑗,𝑙 (2)

138 139 140

𝑉𝑙 ) 𝑙 𝑉𝑙

𝐶 𝐶 𝐷 𝐷 𝑀ℎ,𝑖,𝑗 = ∑𝑓 𝑉𝑖 𝑄𝑖,𝑓,𝑗 (𝑒𝑐𝑚,𝑓,ℎ + ∑𝑑 𝐸𝑑,𝑓 𝑒𝑑,ℎ + 𝐸𝑓𝑊 ∑𝑙 𝑒𝑚𝑓,𝑙,ℎ ∑

(3)

Similarly, the mass of annual air emissions associated with chemical consumption by

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𝑐 each water treatment facility, 𝑀ℎ,𝑖,𝑗 in [g/yr], is calculated using Equation 3. Air emissions from

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chemical manufacturing originate from three sources. The first source is emissions released

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𝐶 directly during the manufacturing of chemical f, 𝑒𝑐𝑚,𝑓,ℎ in [g-emissions/g-chemicals]. The

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second source of emissions is from the combustion of thermal energy to drive chemical

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𝐷 manufacturing, which is the product of the energy consumed from fuel source d, 𝐸𝑑,𝑓 in [MJ/g-

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𝐷 chemical], and emission per unit of thermal energy, 𝑒𝑑,ℎ in [g-pollutant/MJ]. The final source is

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emissions from electricity consumed in chemical manufacturing which is the weighted average

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of the grid emissions, ∑𝑙 𝑒𝑚𝑓,𝑙,ℎ ∑

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to produce a unit of chemicals, 𝐸𝑓𝐶 in [kWh/g-chemical]. This weighting is done according to a

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state’s chemical manufacturing sector size and we assume chemical manufacturing follows the

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nationwide distribution in chemical production.45 The sum of these emissions per unit of

𝑉𝑙 𝑙 𝑉𝑙

in [g-emissions/kWh] multiplied by the electricity consumed

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chemical is then multiplied by the water required to be treated at facility i, Vi in [m3/yr], and the

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chemical dosage, Qi,f [g-chemical/m3]. Additional detail about the methods used to calculate

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chemical emissions can be found in our previous work.46 We also perform sensitivity analyses

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(SI Section 4.0) on assumptions about the geographic distribution of chemical manufacturing and

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binding air pollution regulations.

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Damages from Drinking Water Systems

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To calculate the associated air emission damages from drinking water systems at the

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facility-level, we use AP2,21 EASIUR,47 and the social cost of carbon23 to estimate the damages

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per ton of additional pollutant j occurring in state l, dj,l in [$/g]. In the main manuscript we report

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health and environmental damages from CAPs using AP2. Note that AP2 includes both human

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health and environmental damages of CAPs, but the human health damages are several orders of

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magnitude larger than the environmental damages due to reduced agricultural crop and timber

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sales. The SI reports results using the EASIUR model, which exclusively models human health

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damages. Both AP2 and EASIUR account for atmospheric transformation of pollutants,

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including damages associated with the formation of secondary aerosols. The disagreement

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between AP2 and EASIUR health damage estimates stem from differences in underlying

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atmospheric transport models and atmospheric transformations. Damages from these models are

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calculated in 2014 USD with a value of a statistical life of $8.7 million.48

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Air emission damages associated with electricity consumption are calculated at the

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𝐸𝑙𝑒𝑐 facility-level, 𝐷𝑖,ℎ in [$/yr], by multiplying the amount of electricity consumed at facility i by

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𝑑𝑗,𝑙 (Equation 4). Air emission damages associated with the production of chemicals consumed

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in water treatment are calculated for each state l as the product of 𝑑𝑗,𝑙 and estimated mass of air

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emissions from chemical manufacturing in that state (Equation 5).

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𝐸𝑙𝑒𝑐 𝐸𝑙𝑒𝑐 𝐷ℎ,𝑖 = ∑𝑗 𝑑𝑗,𝑙 𝑀ℎ,𝑖,𝑗

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𝐶 𝐷ℎ,𝑙 = ∑𝑗 𝑑𝑗,𝑙 𝑀𝐶ℎ,𝑖,𝑗 ∑𝑙=𝐿 𝑉

𝑉

(4) (5)

𝑙 𝑙

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The total damages nationwide for treatment train h, Dh in [$/yr], is given by Equation 6.

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𝐸𝑙𝑒𝑐 𝐶 𝐷ℎ = ∑𝑖 𝐷𝑖,ℎ + ∑𝑙 𝐷ℎ,𝑙

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2.2 Benefit-Cost Analysis of Drinking Water Regulations

(6)

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We compare the damages calculated using Equation 6 to the benefits reported in the

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regulatory documentation for Arsenic,30 the Lead and Copper Rules,31 and the Disinfection

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Byproduct Rules.5 Costs (C) considered in these regulatory analyses include technology

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installation and regulatory oversight. The costs do not include damages from embedded air

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emissions, as the EPA did not calculate them during the BCA process. Benefits (B) include

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health benefits and other environmental benefits. The net benefits (N) of a rule are calculated

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using Equation 7.

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𝑁 = 𝐵 − 𝐶 − 𝐷ℎ

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For the three rules that are still in development, we use published estimates of

(7)

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compliance technology costs to calculate the health benefits from improved water quality

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necessary for the rule to provide a net benefit to society.49

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2.3 Evaluating Regulatory Compliance Options

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The EPA recommends two compliance technology options for PFOA/PFOS: reverse

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osmosis or granular activated carbon. In the main analysis laid out in Section 2.1, we model

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plants installing granular activated carbon adsorption processes to comply with the PFOA/PFOS

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health advisory. We repeat the calculations in Section 2.1 using reverse osmosis as the

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compliance technology to explore the difference in damages resulting from selecting an

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alternative technology.

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2.4 Forecasting Emissions from Electricity Consumption The marginal emission factors from electricity generation are expected to decrease as

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coal fired power plants are replaced by natural gas plants and renewable energy sources. This

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transition may, in turn, reduce the embedded air emission damages from drinking water

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treatment. We use EIA Annual Energy Outlook 2017 Reference case with the Clean Power

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Plan50 forecasts of electricity generation, Gk,m [kWh], to calculate national average shares of

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electricity from fuel m (coal, natural gas, diesel, and zero operating emission energy sources) in

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year k between 2015-2050. This reference case assumes that the US upholds its CO2 reduction

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commitments as outlined in the Paris Agreement. We also include two additional cases, the EIA

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AEO Reference case without the Clean Power Plan and the EIA AEO high oil and gas resource

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and technology scenario, as alternative future energy portfolios. We then calculate national

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average emission factor forecasts, eaf,m [g/kWh], over this interval for SO2, NOx, PM2.5, and CO2

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using average emission factors from fuel source coal, natural gas, and diesel.51 We then multiply

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national average emission factor forecasts by the amount of electricity consumed to drive

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baseline and regulatory treatment trains and average damages per mass of air pollution values in

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order to calculate expected damages through 2050 (Equation 8).

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𝑊 𝐷𝑘,ℎ = ∑𝑗(𝑑𝑗 ∑𝑖 𝑉𝑖 ∑𝑔( 𝐸𝑔,ℎ ∗

𝐺𝑘,𝑚 𝑒𝑎𝑓,𝑚 ∑𝑙 𝐺𝑘,𝑚

))

(8)

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Because we use marginal emission factors for the main analysis and average emission factors for

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forecasting, Equation 8 overestimates the damages. We correct for this overestimation, 𝐷̃ 𝑘,ℎ

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[$/yr], by multiplying the ratio of calculated results for 2014 from Equation 5, Dh [$/yr],

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forecasted results for 2014 from Equation 8, Dk,h [$/yr] (Equation 9).

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𝐷̃ 𝑘,ℎ =

𝐷ℎ 𝐷ℎ,𝑘=2014

𝐷𝑘,ℎ (9)

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3.0 Results and Discussion

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3.1 Air Emission Damages from Operating Baseline and Compliant Treatment Trains

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We estimate that baseline operation of water treatment plants consumed 2800 GWh of

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electricity, consumed 1.5 million tons of chemicals, and generated $493 million dollars in air

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emission damages in 2014 (expressed in 2014 dollars and using a value of a statistical life of

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$8.69 million) (Figure 2A, 2C, and 2E). Emissions from chemical manufacturing contributes

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73% of the damages in the baseline treatment train. For comparison, air emission damages

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calculated using EASIUR amount to $533 million ($135 million from electricity generation and

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$398 million from chemical manufacturing) as shown in SI Section 5.2, Figure S1, and Table

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S10 .The damages associated with operating baseline water treatment are several orders of

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magnitude lower than the benefits of avoided illness and death from untreated drinking water.2

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These air emission damages are also several orders of magnitude smaller than the approximately

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100,000 deaths from air emissions that occur annually in the US.52

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Figure 2. Per capita air emission damages associated with operating drinking water treatment

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processes under current and future regulatory scenarios. State-level damages embedded in

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electricity consumption by water treatment processes for the (A) baseline treatment train and the

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(B) regulated treatment train assuming compliance with all promulgated and proposed SDWA

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regulations. State-level damages embedded in chemical consumption by water treatment

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processes for the (C) baseline treatment train and the (D) regulated treatment train. Total air

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emissions damages for the (E) baseline treatment train and the (F) regulated treatment train.

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Emissions and damages are tabulated in SI Tables S8 and S9 and SI Section 5.1. Results

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calculated using EASIUR to price CAP damages can be found in SI Section 5.2, Figure S1, and

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Tables S10 and S11.

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Achieving compliance with the six drinking water regulations increases air emission

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damages by $242 million (in 2014$) annually using the compliance technologies listed in Table

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1 and GAC for PFOA/PFOS removal (Figure 2, B, and D). This represents an increase of 49%

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from the emissions associated with the baseline treatment train. Of this $242 million in

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damages, 76% are damages from chemical manufacturing. Over 84% of these damages, $205

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million (in 2014$), stem from compliance with the PFOA/PFOS Health Advisory at 27,000

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drinking water facilities nationwide. EASIUR modeled air emission damages from regulatory

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compliance estimate that total damages equal $796 million, or an additional $263 million beyond

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baseline damage estimates using EASIUR ($41 million from electricity generation and $222

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million from chemical manufacturing) as shown in SI Section 5.2, Figure S1, and Table S11.

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Emissions and damages increases estimated for compliance with each of the six regulations are

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broken down in SI Section 6.0, Tables S12-S17, and Figures S2-S7.

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3.2 Benefit-Cost Analysis of Drinking Water Regulations

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Table 2. Benefit-Cost analysis for the six drinking water regulations after accounting for

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estimated air emission damages. Benefits

Contaminant Finalized Rules Arsenic30 DBP

5

Lead & Copper31

Costs/Damages Compliance Electricity Costs Damages 3 ($/m in 2014$)

Net Chemical Damages

0.14

0.16

0.0005

0.000002

-0.023

3.13

1.08

0.0013

0.0080

2.04

8.36

1.35

0.0006

0.0003

7.01

Rules Under Consideration Chromium (VI)

≥0.25*

0.2049

0.024

0.0014

≥0

Strontium

≥0.43*

0.4053

0.0008

0.042

≥0

PFOA/PFOS**

≥0.61*

0.6049

0.0015

0.0078

≥0

*Rules that are under consideration do not have published estimates for their benefits and compliance costs. **Using Granular Activated Carbon as the compliance technology.

269 270

For the three finalized rules (Arsenic, DBPs, and Lead and Copper), the signs on the

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benefit-cost analysis do not change with the inclusion of air emission damages (Table 2). The

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DBP and Lead and Copper rules had large benefits to society, and accounting for air emissions

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damages does not change this conclusion. The arsenic rule was a net cost to society without

274

incorporating air emissions from drinking water; including air emissions in the benefit-cost

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analysis only increases the cost.

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For the three rules that are not yet finalized, Table 2 presents the minimum benefits

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required given estimates of air emission damages from this analysis and literature-based

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compliance technology costs.49, 53 On a per cubic meter basis, air emission damages contribute 2-

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11% of the total costs to society for these rules. Air emissions are therefore a small, but non-

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negligible contributor to these overall costs. The benefits required for these rules to impart net

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social benefits range from $0.25/m3 to $0.61/m3 (in 2014$).

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There are several unquantifiable co-benefits of adopting the six drinking water

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regulations that are not accounted for in this analysis. These include the reduction of unregulated

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contaminant concentrations associated with the advanced treatment technologies that are

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installed to comply with these rules. There is also the possibility that, in the process of

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complying with new water quality regulations, monitoring and enforcement of existing water

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quality regulations is improved.

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3.3 Evaluating Regulatory Compliance Options

289 290

Figure 3. Air emission damages from reverse osmosis and granular activated carbon treatment

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for PFOA/PFOS removal at non-compliant drinking water facilities across the United States

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using state-level marginal emissions factors for NOx, SO2, and CO2 and state-level average

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emissions factors for PM2.5. The error bars show the uncertainty in the location and presence of

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binding regulations affecting emissions from the chemical manufacturing sector (SI Section 4.0)

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and Tables S4-S7.

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Quantifying the air emission damages of drinking water treatment processes can also assist in compliance technology selection. Of the two compliance options for PFOA/PFOS

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removal, reverse osmosis is the highest damage alternative (Figure 3). Using reverse osmosis to

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comply with the PFOA/PFOS standards imposes air emission damages of $1.2 billion annually

300

(in 2014$). The use of GAC to achieve compliance with PFOA/PFOS imposes air emission

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damages of $205 million/yr (in 2014$), a sixth of the damages from reverse osmosis. The

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primary source of air emission damages from RO is the electricity used to drive the process,

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rather than from emissions embedded in chemical consumption. In contrast, granular activated

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carbon leads to more damages from chemical manufacturing than reverse osmosis, with

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subsequently more uncertainty.

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Reverse osmosis and granular activated carbon have different removal efficiencies for

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PFOA/PFOS, with RO producing higher quality water. This sets up trade-off between reducing

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health risks from PFOA/PFOS in drinking water and minimizing the environmental and health

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risks from criteria air pollutants and greenhouse gasses. To account for this additional $1.0

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billion in air emission damages annually, reverse osmosis would need to save an additional 120

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statistical lives through PFOA/PFOS concentration reduction. These additional statistical lives

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could also be saved by the co-benefits of RO by producing higher quality water.

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3.4 Future Air Emission Damages from Electricity Consumed in Drinking Water Treatment

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Figure 4. Projected air emission damages from electricity generated to treat US drinking water

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with the baseline treatment train and the additional emissions that result from compliance with

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current and proposed drinking water standards. The grid mix follows the AEO 2017 Reference

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case with the Clean Power Plan. Forecasts for the AEO 2017 Reference case without the Clean

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Power Plan and the High oil and gas resource and technology scenario differ by less than 7%

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(details reported in SI Section 7.0). N.B. That this figure does not include damages resulting

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from the electricity consumed during chemical manufacturing.

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As the grid evolves to rely less on fossil fuel sources, damages from air emissions are

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expected to decrease (Figure 4). By 2050, annual damages associated with emissions from

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electricity generation that result from compliance with these six standards decreases by $19

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million per year from the 2015 level of $40 million. This reduction in damages from electricity

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will lower the required benefits presented in Table 2 to achieve net benefits from these drinking

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water rules. Projected air emission damages for two alternative electricity grid scenarios,

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including scenarios without the Clean Power Plan and with high natural gas use differ by less

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than 7% (SI Section 7.0 and Figure S8). The robustness of these results to changes in the

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electricity mix reflect the relatively small fraction of damages that originate from electricity

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consumption.

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4.0 Implications

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Stronger epidemiological evidence of health impacts from contaminated water, enhanced

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public awareness of water quality issues, and improved analytical techniques for detecting

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aqueous contaminants are each drivers for stricter water quality regulations.1, 54 While the

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counter-argument to installing the advanced treatment technologies necessary for compliance has

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historically been cost, we propose that the very real risks of air emission damages associated

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with increased electricity or chemical consumption of water treatment processes should also be

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considered. These incremental air emission damages may outweigh the incremental benefits of

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cleaner water enabled by stricter drinking water regulatory limits, but establishing this balance of

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cost and benefits is difficult to establish a priori.

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Given that air emission damages are difficult to establish a priori and useful in informing

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regulatory concentration limits, we conclude that there are merits to regulatory assessment

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processes explicitly considers the life-cycle tradeoffs between improved water quality and

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reduced air emissions. This process may inform the selection of concentration limits that

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maximize human health benefits, technologies for regulatory compliance, or investment

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priorities in the water, chemical, and electricity generation space. While performing this analysis

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will increase EPA workload, screening approaches such as Economic Input/Output LCA may

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allow the EPA to assess the need for the more robust analysis described in this manuscript.55

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Adapting the regulatory assessment process to include life-cycle air emissions may also

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broaden the scope of environmental justice analyses. This analysis demonstrates that spatial

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distribution of the damages, and not simply the water quality benefits, varies across the United

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States and should be considered in evaluating regulations. Areas with high-levels of coal-fired

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electricity generation or chemical manufacturing may experience damages from air emissions in

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excess of benefits from improved drinking water quality. Performing spatially-resolved air

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emissions analyses allows the EPA to quantify these trade-offs as part of their standard

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environmental justice analyses.

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Finally, this analysis supports the ongoing transition from single-media focused

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regulations (e.g. drinking water) towards more holistic analyses that account for the

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countervailing risks analyzed in this paper. Previous examples of the EPA moving to holistic

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regulatory activity includes the cluster rules for the pulp and paper industry56 and Executive

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Order (EO) 13211 mandating that all regulations, including drinking water regulations, undergo

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an energy inventory if they are deemed “economically significant.”43 Unfortunately, it is not

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standard practice for analyses performed under EO 13211 to assess emissions associated with

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this electricity generation or incorporate the damages into benefit-cost analyses performed under

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EO 12866. Even if damages from the emissions associated with electricity generation were

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included in EPA BCAs for drinking water treatment, the emissions from chemical manufacturing

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would be overlooked. As chemical manufacturing damages contribute roughly three times as

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much as electricity generation, their inclusion is important in ensuring a comprehensive analysis

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of these trade-offs.

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In short, more rapid adoption of environmental regulatory frameworks that account for

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inter-sectoral and cross-media risk trade-offs should be a priority at both the national and state

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levels.

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Acknowledgements

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This work was supported by the National Science Foundation under award number CBET-

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1554117.

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Supporting Information

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The supporting information contains descriptions of 1) the six drinking water standards with

379

compliance modeled in this analysis; 2) data sources; 3) drinking water treatment unit process

380

description and inputs; 4) chemical manufacturing location sensitivity analyses; 5) emissions and

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damages from drinking water treatment using AP2 and EASIUR; 6) emissions and damages

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from the individual drinking water standards; and 7) air emission damages using alternative grid

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forecasts.

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Nomenclature

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A:

Per capita annual water consumption [m3/person·yr]

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B:

Benefits from a drinking water regulation [$/yr]

387

C:

Compliance costs from a drinking water regulation [$/yr]

388

D:

Air emission damages for drinking water treatment [$/yr]

389

̃: 𝐷

Corrected damages forecast [$/yr]

390

d:

Damages per unit of NOx, SO2, PM2.5, and CO2 [$/g]

391

E:

Energy consumption [kWh/m3], [kWh/g-chemical], or [MJ/g-chemical]

392

e:

Emissions factor per unit of energy [g/kWh] or [g/MJ]

393

G:

Annual electricity generation [kWh]

394

M:

Annual mass of NOx, SO2, PM2.5, or CO2 emissions [g/yr]

395

N:

Net benefits or costs from a drinking water regulation [$/yr]

396

Pop:

Population served by a facility [people]

397

Q:

Chemical dosage [g-chemical/m3]

398

V:

Annual value of products from the chemical manufacturing sector [$]

399

V:

Annual water production [m3/yr]

400

W:

Electricity consumption for water treatment process [kWh/m3]

401

Subscripts

402

af:

Average emissions factor

403

cm:

Chemical manufacturing

404

d:

Thermal fuel

405

f:

Chemical

406

g:

Unit process

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h:

Treatment train (baseline or newly-regulated)

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i:

Drinking water facility

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j:

Air pollutant (NOx, SO2, PM2.5, or CO2)

410

k:

Year

411

l:

State

412

m:

Fuel source for electricity generation

413

\mf:

Marginal emissions factor

414

PC:

per capita

415

served:

Population served by a facility

416

Superscripts

417

C

:

From chemical manufacturing

418

D:

From thermal fuel combustion

419

Elec

420

W

421

References

422 423 424 425 426 427 428 429 430 431 432 433 434 435

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